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Mercury
Mercury, also known as quicksilver or hydrargyrum, is a chemical element with the symbol Hg and atomic number 80. A heavy, silvery d-block metal, mercury is one of five metallic chemical elements that are liquid at or near room temperature and pressure, the others being cesium, francium, gallium, and rubidium. Mercury is the only metal that is liquid at standard conditions for temperature and pressure; the only other element that is liquid under these conditions is bromine. With a melting point of −38.83 °C and boiling point of 356.73 °C, mercury has one of the narrowest ranges of its liquid state of any metal. Mercury is used in thermometers, barometers, manometers, sphygmomanometers, float valves, and other scientific apparatus, though concerns about the element's toxicity have led to mercury thermometers and sphygmomanometers being largely phased out in clinical environments in favour of alcohol-filled, digital, or thermistor-based instruments. It remains in use in a number of other ways in scientific and scientific research applications, and in amalgam material for dental restoration. It is used in lighting: electricity passed through mercury vapour in a phosphor tube produces short-wave ultraviolet light which then causes the phosphor to fluoresce making visible light Characteristics Mercury is a heavy, silvery-white metal. As compared to other metals, it is a poor conductor of heat, but a fair conductor of electricity. Mercury has an exceptionally low melting temperature for a d-block metal. A complete explanation of this fact requires a deep excursion into quantum physics, but it can be summarized as follows: mercury has a unique electronic configuration where electrons fill up all the available 1s, 2s, 2p, 3s, 3p, 3d, 4s, 4p, 4d, 4f, 5s, 5p, 5d and 6s subshells. As such configuration strongly resists removal of an electron, mercury behaves similarly to noble gas elements, which form weak bonds and thus easily melting solids. The stability of the 6s shell is due to the presence of a filled 4f shell. An f shell poorly screens the nuclear charge that increases the attractive Coulomb interaction of the 6s shell and the nucleus. The absence of a filled inner f shell is the reason for the much higher melting temperature of cadmium. Metals such as gold have atoms with one less 6s electron than mercury. Those electrons are more easily removed and are shared between the gold atoms forming relatively strong metallic bonds. At the melting point (-38.86 °C) its density is6 14.1 g/cm3. Mercury dissolves to form amalgams with gold, zinc and many other metals. Because iron is an exception, iron flasks have been traditionally used to trade mercury. Other metals that do not form amalgams with mercury include tantalum, tungsten and platinum. When heated, mercury also reacts with oxygen in air to form mercury oxide, which then can be decomposed by further heating to higher temperatures. Since it is below hydrogen in the reactivity series of metals, mercury does not react with most acids, such as dilute sulphuric acid, though oxidizing acids such as concentrated sulphuric acid and nitric acid or aqua regia dissolve it to give sulphate, nitrate, and chloride salts. Like silver, mercury reacts with atmospheric hydrogen sulphide. Mercury even reacts with solid sulphur flakes, which are used in mercury spill kits to absorb mercury vapours (spill kits also use activated carbon and powdered zinc). Value The base value of each unit of ranges between 10 and 15Ð per unit, with up to 2 units being found at any one time. Presence on Mars: Very Rare Category:Chemical elements